Adsorptive removal and mechanism of monocyclic aromatics by activated carbons from water: Effects of structure and surface chemistry

Abstract

This paper reports adsorption behaviors of monocyclic aromatics from water onto different pore-size activated carbons and HNO3-modified activated carbon fiber felt, and modelling of experimental data by the Langmuir, the Freundlich, the Dubinin-Radushkevich and the Temkin isotherms. To study the adsorption mechanism, the maximum uptakes of compounds by activated carbons in the Langmuir model were correlated with the structure of activated carbons. The results show that the Langmuir isotherm is superior to other isotherms and the Langmuir model can approximately describe adsorption behaviors of activated carbons for aniline, phenol, and pyridine. For high-concentration adsorption, activated carbon’s micropore volume has a positive effect on adsorption capacity of compounds, and micropore filling mainly happens. The uptake of aniline and phenol by activated carbon is obviously higher than that pyridine, which is ascribed to their low solubility. The surface acidic groups (mainly oxygen-containing groups) of activated carbon fiber felt obviously decrease adsorption capacity for aromatics due to a decrease in dispersion interaction between activated carbon’s surface and aromatics. The results show that in order to effectively remove high-concentration aromatics from water, effects of micropore vlome and surface acidic groups of activated carbons need to be considered, compared and analyzed, and micropore volume of activated carbon should usually be given priority to.